The sad truth is that man's real life consists of a complex of inexorable opposites - day and night, birth and death, happiness and misery, good and evil. We are not even sure that one will prevail against the other, that good will overcome evil, or joy defeat pain. Life is a battleground. It always has been and always will be; and if it were not so, existence would come to an end.

The Collected works (ed. 1976)